1. Field of the Invention
The present invention relates to a method of fixing an optical fiber array to a substrate, which can fix the optical fiber array to the substrate precisely in a thickness direction.
2. Related Art Statement
FIG. 6 is a schematic view for explaining a known method of fixing an optical fiber array to a substrate. In FIG. 6, an optical fiber array 57 comprises a V-groove substrate 54 having a plurality of V-grooves 53 used for fixing optical fibers 52, a fix substrate 55 for fixing the optical fibers 52 in the V-grooves 53, and a pair of guide grooves 56 arranged at both ends of the V-grooves 53 of the V-groove substrate 54. When the optical fiber array 57 having the construction mentioned above is fixed to an element mount substrate 51, it is necessary to set precisely a position of the optical fiber 52 with respect to the element mount substrate 51 i.e. a distance A in a thickness direction. This is because, as shown in FIG. 6, the optical fiber array 57 and an optical element 58 such as an optical waveguide or the like must be fixed on the element mount substrate 51 in such a manner that optical axes of the optical element 58 are optically made identical with those of the optical fibers 52 of the optical fiber array 57.
In the known embodiment mentioned above, in order to set precisely the distance A in the thickness of the optical fiber array 57 and a distance B in the thickness direction of the optical element 58, they are worked with reference to the surfaces, to which the element mount substrate 51 is contacted, in such a manner that distances from those reference surfaces are made equal to the distances A and B. In this case, the distance B in the thickness direction of the optical element 58 can be worked relatively easily to a precise value since a shape to be worked is simple. However, it is difficult to work the distance A in the thickness direction of the optical fiber array to a precise value, since a shape to be worked is complicated.
Therefore, the optical axes of the optical fiber array 57 and the optical element 58 are made identical with each other in such manner that a light transmitted through both of the optical fiber array 57 and the optical element 58 is monitored while they are moved relatively on the element mount substrate 52 and they are fixed to the element mount substrate 51 at which a power of the monitored light is largest. In this case, if the distance A in the thickness direction of the optical fiber array 57 is inaccurate as mentioned above, a space is generated between the element mount substrate 51 and the optical element 58 or the optical fiber array 57, and thus it is necessary to fill adhesives into the space. Therefore, a stress due to a shrinkage or expansion of the adhesives is generated in the thickness direction, and thus it is feared that a reliability of the optical connection is deteriorated.